Systems and methods for trimming dental aligners

ABSTRACT

Systems and methods for trimming dental aligners include a cut line system for identifying a first point and a second point based on a line around tooth (LAT) for a tooth of a model representative of a dentition of a user, where the first point is disposed on a tooth-gingiva interface of the tooth. The cut line system defines a cut plane at a distance from the first point toward the second point, where the cut plane intersects a line between the first point and the second point, identifies a plurality of points on the LAT based on the cut plane, defines a cut line based on the plurality of points on the LAT and the first point, and controls a cutting system to cut the dental aligner along the cut line.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/181,929, filed Feb. 22, 2021, which is a continuation-in-part of U.S.patent application Ser. No. 16/292,779, filed Mar. 5, 2019, the contentsof each of which are incorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates generally to intraoral devices. Morespecifically, the present disclosure relates to trimming or cuttingdental aligners and other intraoral devices.

Dental aligners may be worn by a patient receiving orthodontictreatment. Some dental aligners may be fabricated by thermoformingaligner material to a dental mold. After thermoforming the alignermaterial to a dental mold, the formed aligner is cut and removed fromthe dental mold so that the aligner can be worn by the patient.

SUMMARY

At least one embodiment relates to a method of cutting a dental aligner.The method includes identifying a first point and a second point basedon a line around tooth (LAT) for a tooth of a model representative of adentition of a user. The first point is disposed on a tooth-gingivainterface of the tooth. The method further includes defining a cut planeat a distance from the first point toward the second point, where thecut plane intersects a line between the first point and the secondpoint, identifying a plurality of points on the LAT based on the cutplane, defining a cut line based on the plurality of points on the LATand the first point, and controlling a cutting system to cut the dentalaligner along the cut line.

Another embodiment relates to a system for cutting a dental aligner. Thesystem includes a cut line system and a cutting system. The cut linesystem is configured to identify a first point and a second point basedon a line around tooth (LAT) for a tooth of a model representative of adentition of a user. The first point is disposed on a tooth-gingivainterface of the tooth. The cut line system is further configured todefine a cut plane at a distance from the first point toward the secondpoint, where the cut plane intersects a line between the first point andthe second point, identify a plurality of points on the LAT based on thecut plane, and define a cut line based on the plurality of points on theLAT and the first point. The cutting system includes a cutting toolconfigured to cut the dental aligner along the cut line.

Another embodiment relates to a non-transitory computer readable mediumstoring instructions that, when executed by a processor, cause theprocessor to perform operations. The operations include identifying afirst point and a second point based on a line around tooth (LAT) for atooth of a model representative of a dentition of a user, defining a cutplane at a distance from the first point toward the second point, wherethe cut plane intersects a line between the first point and the secondpoint, identifying a plurality of points on the LAT based on the cutplane, and defining a cut line for cutting a dental aligner based on theplurality of points on the LAT and the first point.

This summary is illustrative only and is not intended to be in any waylimiting. Other aspects, inventive features, and advantages of thedevices or processes described herein will become apparent in thedetailed description set forth herein, taken in conjunction with theaccompanying figures, wherein like reference numerals refer to likeelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system for generating dentalaligners, according to an illustrative embodiment.

FIG. 2 is a top view of a model of a user's dentition, according to anillustrative embodiment.

FIG. 3A and FIG. 3B depict example views of a contour with pointsarranged along the surface, according to illustrative embodiments.

FIG. 4A and FIG. 4B depict the labial and lingual sides of a model of auser's dentition, respectively, according to an illustrative embodiment.

FIG. 5 is a simplified top-down diagram of a plurality of teeth within amodel of a user's dentition, according to an illustrative embodiment.

FIG. 6 is a perspective view of a model of a user's dentition focused onthe interproximal region between two teeth in the model, according to anillustrative embodiment.

FIG. 7 is a front perspective view of a model of a user's dentition,according to an illustrative embodiment.

FIG. 8 is a back perspective view of one side of a model of a user'sdentition, according to an illustrative embodiment.

FIG. 9 is a back perspective view of another side of a model of a user'sdentition, according to an illustrative embodiment.

FIG. 10 is a rear perspective view of a model of a user's dentition,according to an illustrative embodiment.

FIG. 11 is a back perspective view of rear molars of a model of a user'sdentition, according to an illustrative embodiment.

FIG. 12 is a flowchart of a method for defining a cut line, according toan illustrative embodiment.

FIG. 13 is a flowchart of a method of cutting a dental aligner,according to an illustrative embodiment.

FIG. 14 is an illustration of a dental aligner fabricated using thesystem for generating dental aligners of FIG. 1 , according to anillustrative embodiment.

FIG. 15 is an illustration of a model of a user's dentition, accordingto an illustrative embodiment.

FIG. 16 is an illustration of the model of FIG. 15 including a cut line,according to an illustrative embodiment.

FIG. 17 is another illustration of the model of FIG. 15 including thecut line, according to an illustrative embodiment.

FIG. 18 is an illustration of a model of a user's dentition, accordingto another illustrative embodiment.

FIG. 19 is an illustration of the model of FIG. 18 including a cut line,according to an illustrative embodiment.

FIG. 20 is an illustration of a model of a user's dentition including acut line at a first offset distance, according to an illustrativeembodiment.

FIG. 21 is an illustration of a model of a user's dentition including acut line at a second offset distance, according to an illustrativeembodiment.

FIG. 22 is an illustration of a model of a user's dentition includinginterproximal virtual filler, according to an illustrative embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate certain exemplaryembodiments in detail, it should be understood that the presentdisclosure is not limited to the details or methodology set forth in thedescription or illustrated in the figures. It should also be understoodthat the terminology used herein is for the purpose of description onlyand should not be regarded as limiting.

Referring generally to the figures, described herein are systems andmethods for trimming intraoral devices, such as dental aligners. A modelanalyzer is configured to receive a model representing athree-dimensional impression of a user's dentition which is used forforming an intraoral device, such as a dental aligner. A gingival lineextractor is configured to identify a gingival line. The gingival lineis defined by a juncture between the tooth and a gum. A cut linedeterminer selects points in the gingiva within the model for defining acut line. When a plurality of points for the cut line are selected, thecut line determiner defines the cut line by joining the plurality ofpoints. A cutting system controller controls a cutting tool of a cuttingsystem to cut the intraoral device along the cut line to prepare theintraoral device for use. While the present disclosure primarily refersto the fabrication of dental aligners, it is noted that the presentdisclosure is not limited to fabricating only dental aligners. Rather,the present disclosure may be applied to fabricating other intraoraldevices such as, but not limited to, mouth guards, retainers, expansionaligners, or other intraoral devices that are cut from a mold.Accordingly, it will be appreciated that any system or process disclosedherein can also be used to fabricate intraoral devices other than dentalaligners.

Referring now to FIG. 1 , an embodiment of a system 100 for fabricatingdental aligners is shown. The system 100 is shown to include a cut linesystem 102, a dentition scanning system 104, and a cutting system 106.The dentition scanning system 104 includes any device, component, orgroup of devices or components configured to generate dentition scans108. The dentition scans 108 may be digital scans of a physical dentalimpression (e.g., captured by a dental technician, a dentist, a user ofa dental aligner). The dentition scans 108 may be direct scans of apatient's dentition. Hence, the dentition scans 108 may be direct scansof a patient's dentition captured by scanning the patient's dentitionwith a three-dimensional camera, or the dentition scans 108 may beindirect scans of the patient's dentition captured by scanning aphysical model or impression of the patient's dentition. In eitherembodiment, the dentition scans 108 are three-dimensionalrepresentations of a patient's dentition. The dentition scans 108 may beused for fabricating a dental aligner, such as the dental aligner 130shown in FIG. 14 , as described in greater detail below.

In some implementations, the cut line system 102 may be embodied as orinclude a processing circuit which includes a processor 110 and memory112. The processor 110 may be a general purpose single- or multi-chipprocessor, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. A general purpose processor maybe a microprocessor, or, any conventional processor, controller,microcontroller, or state machine. The processor 110 also may beimplemented as a combination of computing devices, such as a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration. In some embodiments, particular processes and methods maybe performed by circuitry that is specific to a given function.

The memory 112 (e.g., memory, memory unit, storage device) may includeone or more devices (e.g., RAM, ROM, EPROM, EEPROM, optical diskstorage, magnetic disk storage or other magnetic storage devices, flashmemory, hard disk storage, or any other medium) for storing data and/orcomputer code for completing or facilitating the various processes,layers and circuits described in the present disclosure. The memory 112may be or include volatile memory or non-volatile memory, and mayinclude database components, object code components, script components,or any other type of information structure for supporting the variousactivities and information structures described in the presentdisclosure. According to an illustrative embodiment, the memory 112 iscommunicably connected to the processor 110 via a processing circuit andincludes computer code for executing (e.g., by the processing circuit orthe processor 110) the processes described herein.

The memory 112 may store various modules or be comprised of a system ofcircuits. The circuits may include hardware, memory, and/or othercomponents configured or implemented to execute various functions. Thememory 112 may store a treatment planner 114, a model generator 116, anda model analyzer 118. The treatment planner 114 may be a circuitdesigned or implemented to perform various functions corresponding togenerating a treatment plan for the user's dentition (e.g., based on thedentition scans 108). The model generator 116 may be configured togenerate a model based on the generated treatment plan. The model may bea three-dimensional representation of the user's dentition at variousintervals (e.g., at the start of the treatment plan and at variousintervals throughout the treatment plan). The model analyzer 118 may beconfigured to analyze the models generated via the model generator 116for fabricating dental aligners 130.

In various embodiments, the treatment planner 114 is configured toproduce, generate, assemble, compile, or otherwise create a treatmentplan for moving various teeth of a user's dentition. The treatment planmay be a series of movements for teeth of a user's dentition from astarting arrangement to an ending arrangement. The treatment plan may begenerated by or through use of the treatment planner 114. In someembodiments, a dental technician or professional uses the treatmentplanner 114 to generate the treatment plan by manipulating individualteeth or groups of teeth shown in models based on the dentition scans108. For instance, the treatment planner 114 may present models based onthe dentition scans 108 from the dentition scanning system 104 to thedental professional, who then can manipulate various teeth within thedentition scans 108.

The treatment planner 114 is configured to generate various stages ofthe treatment plan to move the teeth from the starting position (e.g.,their current position as represented within the dentition scan 108) toa final position selected or provided by the dental professional. Insome embodiments, the treatment planner 114 is configured to create thetreatment plan without the assistance of a dental professional. Forinstance, the treatment planner 114 may analyze the dentition scans 108to align the teeth with a dental arch fitted to the teeth. The treatmentplanner 114 may then generate various stages of the treatment plan tomove the teeth from the starting position to the final position.

The model generator 116 is configured to generate models of the user'sdentition at the various stages of the treatment plan generated by orusing the treatment planner 114. The model generator 116 generates aplurality of models including an initial model, a final model, and atleast one intermediate model. The initial model corresponds to a firststage of the treatment plan. The final model corresponds to a finalstage of the treatment plan. Each intermediate model corresponds to anintermediate stage of the treatment plan.

In various instances, the user is provided a dental aligner 130 to beworn at each stage of the treatment plan for a predetermined duration(e.g., one week, two weeks, one month). The dental aligners 130 areconstructed from a material thermoformed to a physical model and worn inthe user's mouth. The dental aligners 130 apply a force on at least oneof the user's teeth to move at least one tooth according to thetreatment plan.

In some embodiments, each stage of the treatment plan includes more thanone dental aligner 130 having the same shape but having a differentthickness or being constructed of a different material (e.g., a harderor softer material). For example, the treatment plan can specify thatthe user wears the softest dental aligner in a first sub-stage, followedby a dental aligner of medium hardness, followed by the hardest dentalaligner.

The dental aligners 130 are trimmed to fit comfortably within the user'smouth. The dental aligners 130 are trimmed to include representations ofthe user's teeth and a portion of the user's gums. As described ingreater detail below, the model analyzer 118 is configured to determinea cut line for the dental aligners 130 and the model analyzer 118 isconfigured to control the cutting system 106 to cut the dental aligners130 along the cut line.

The model analyzer 118 may include a tooth identifier 120. The toothidentifier 120 may be a sub-circuit of the model analyzer 118. Whileshown as included within and a component of the model analyzer 118, insome embodiments, the tooth identifier 120 is separate from the modelanalyzer 118. The model analyzer 118 may also include a gingival lineextractor 122, a cut line determiner 124, and a cutting systemcontroller 126. The gingival line extractor 122, cut line determiner124, and cutting system controller 126 may each be sub-circuits of themodel analyzer 118 or, in some embodiments, may be separate from themodel analyzer 118. In some embodiments, some of the components orsub-circuits may be combined or further separated.

Referring now to FIG. 1 and FIG. 2 , the tooth identifier 120 isconfigured to extract the teeth 200 and gingiva 202 from the model 204generated via the model generator 116. Specifically, FIG. 2 depicts atop view of a model 204 of a user's dentition, according to anillustrative embodiment. While described herein as teeth 200 and gingiva202 with reference to the model 204, it is noted that the teeth 200refer to a teeth portion 200 of the model 204 which correspond to teethwithin the user's dentition, and gingiva 202 refer to a gingiva portion202 of the model which corresponds to gingiva within the user'sdentition. The tooth identifier 120 can be configured to identify theteeth within the model using a teeth identification algorithm. The teethidentification algorithm may identify various characteristics within themodel which are consistent with teeth 200, such as surface contours ofcrowns, separation or gaps in the interproximal region (e.g., the spacebetween teeth 200), etc. The tooth identifier 120 can be configured toidentify the teeth 200 within the model 204 and identify the remainingportions of the model 204 which are not teeth 200 as gingiva 202.

The tooth identifier 120 may be configured to label the teeth 200according to an identification system, such as a numbering system. Thenumbering system can be the universal numbering system, the Palmernumbering system, the FDI numbering system, etc. The numbering systemmay be used for ordering teeth 200 and locating end teeth, as describedin greater detail below. The tooth identifier 120 may be configured toassign numbers to various teeth 200 based on their location within theuser's dentition. Each identifier or number may be particular to aspecific location of a tooth within a standard (e.g., fully developed)dentition. The tooth identifier 120 may be configured to generate anobject (OBJ) file including each of the teeth 200 and gingiva 202, witheach of the teeth 200 and gingiva 202 being represented as separateobjects within the OBJ file.

In the model 204, each of the teeth 200 and the gingiva 202 may bepositioned in an orientation along the user's dentition. The toothidentifier 120 may be configured to generate a global axis for theuser's dentition. The global axis may be an axis defined along thecenter of mass of the user's dentition (extending in the labial/lingualdirection, in the cranial/caudal direction, etc.), along the front-mostor rear-most points of the user's dentition, etc. The tooth identifier120 may be configured to define or identify orientation datacorresponding to an orientation of each of the objects with respect tothe global axis. Each object may be separately defined within the OBJfile and include the orientation data.

In some embodiments, the tooth identifier 120 is configured to identifya reference point 206 for each of the teeth 200 in the model 204. Thereference points 206 may be used for defining the cut line, as describedin greater detail below. In some embodiments, the reference points 206may be the centroids, or center of mass, for each of the teeth 200. Asused herein, reference point and centroid are used interchangeably,though it will be appreciated that a reference point does not need to bea centroid of a tooth or related to a center of mass of a tooth. Thetooth identifier 120 may be configured to determine a two-dimensionalcentroid (e.g., from the overhead view shown in FIG. 2 ) for each of theteeth 200. In some embodiments, the tooth identifier 120 may beconfigured to connect each of the centroids 206 to generate a dentalarch line 208. The dental arch line 208 may also be used for definingthe cut line.

The gingival line extractor 122 is configured to identify a gingivalline 210 for the model 204. The gingival line 210 is defined as thejuncture or interface between the teeth 200 and gingiva 202. Thegingival line extractor 122 may be configured to identify the gingivalline 210 by identifying a location where the teeth 200 and gingiva 202meet. As described above, the tooth identifier 120 may be configured toidentify a location of the teeth 200 within the model 204, and mayidentify the location of the gingiva 202 based on which portions of themodel 204 are not identified as teeth 200. Similarly, the gingival lineextractor 122 may identify the gingival line 210 based on where theportions of the model 204 identified as teeth 200 meet portions of themodel 204 identified as gingiva 202.

The cut line determiner 124 is designed or implemented to define a cutline 212 for the dental aligner 130. The cut line 212 is a line or pathwhich extends around the model 204 and defines a travel path for acutting tool 128 of the cutting system 106. As described in greaterdetail below, the cutting system controller 126 may control the cuttingtool 128 (e.g., various actuators which manipulate or otherwise move thecutting tool 128) to move along the cut line 212 to cut the dentalaligner 130 from the model 204.

The cut line determiner 124 is configured to generate points for the cutline 212. “Points,” as used herein, refers to individual points thatmake up the cut line 212. Each point is generated by the cut linedeterminer 124. FIG. 3A and FIG. 3B depict example views of a contour300 with points 302 arranged along the surface of the contour 300. Asshown in FIG. 3A and FIG. 3B, the cut line determiner 124 may beconfigured to generate a sufficient number of points 302 to capturecontours 300 in the model 204 (e.g., on or along the surface of themodel 204). In FIG. 3A, the contour 300 has insufficient points 302 toaccurately capture the contour 300, as the inflection along the contour300 does not include any points 302 and is therefore not taken intoaccount by the cut line determiner 124 when generating a cut line. InFIG. 3B, the cut line determiner 124 has generated a sufficient numberof points 302 to accurately capture the contour 300 of the model (e.g.,by having at least one point 302 within the inflection of the contour300). Embodiments using more points can provide for a more accurate cutof the aligner 130. Each point may be defined within a coordinate systemwith respect to, for instance, the global axis (e.g., x,y,z coordinates)to define the cut line 212, as described in greater detail below.

The cut line determiner 124 joins the points 302 together to form thecut line 212. The cut line determiner 124 may generate points 302 byidentifying a location in the gingiva 202 a threshold distance from thegingival line 210. The threshold distance from the gingiva 202 is afunction of the amount of space of the dental aligner 130 which is tocontact, cover, or otherwise interface with the gingiva (a gingivaportion 202 of the dental aligner 130). In various implementations, thethreshold distance may be relatively small such that little to nogingiva of the user's dentition is covered by or interfaces with thedental aligner 130. In such embodiments, the dental aligner 130 may notbe as comfortable and may not be easily anchored within the user'smouth. In various implementations, the threshold distance may berelatively large such that a significant amount of gingiva of the user'sdentition is covered by or interfaces with the dental aligner 130. Insome embodiments, the threshold distance results in a dental aligner 130that covers or interfaces with a minimal amount of the user's gingiva.Accordingly, it will be appreciated that the dental scan or impressioncan accurately capture the gingiva of the user, such that the trimmeddental aligner 130 conforms to the gingiva of the user.

In various implementations, the threshold distance may fall within arange of 0.5 mm and 4.0 mm. In such implementations, a relatively smallamount of gingiva is covered by or interfaces with the dental aligner130, which may balance anchoring and comfort of the dental aligner 130with difficulty in accurately capturing gingiva in the dentition scan108. Thus, where the threshold distance falls within the range of 0.5 mmand 4.0 mm, the cut line determiner 124 generates points in the gingiva202 for the cut line 212 a distance from the gingival line 210 within arange (such as between 0.5 mm and 4.0 mm beneath the gingival line 210).Such a range may provide for sufficient anchoring of the dental aligner130 by the user's gingiva while still limiting the amount of gingivacovered by or interfacing with the dental aligner (thus limiting thelevel of detail required for accurately representing the gingiva in thedentition scans and the aligner 130).

In some embodiments, the cut line determiner 124 generates points 302 byidentifying locations that are a distance from the gingival line 210 andin regard to the reference points 206. For instance, the cut linedeterminer 124 may identify locations for points aligned with both thereference point 206 and the gingival line 210 (e.g., moving radiallyoutward from the reference point 206).

In some embodiments, the cut line determiner 124 generates points byidentifying locations that are a distance (e.g., 1.5 mm) from thegingival line 210 without regard to the reference points 206. Forinstance, the cut line determiner 124 computes or determines the cutline 212 based on the gingival line 210. As described in greater detailbelow, the cut line determiner 124 may offset the cut line 212 from thegingival line 210 by identifying points in the gingiva 202 a distancefrom the gingival line 210 along the surface of the model 204 to createthe cut line 212.

Referring now to FIG. 4A and FIG. 4B, the cut line determiner 124 isconfigured to generate points based on the lingual and labial lowestpoint of the tooth 200/gingiva 202. Specifically, FIG. 4A and FIG. 4Bdepict the labial and lingual side of the model 204, respectively. Thecut line determiner 124 is configured to identify the lingual and labiallowest points 400 for each tooth 200 in the model 204. The cut linedeterminer 124 is configured to determine the labial and lingual sidesof each tooth 200 within the model 204 based on the orientation datacorresponding to each object within the OBJ file. The cut linedeterminer 124 is configured to define a line-around-tooth (LAT) foreach tooth. The LAT may be defined based on the intersection of theteeth 200 and gingiva 202. Hence, the LAT for each tooth 200 may extendaround the tooth 200 at the gingival line 210 for the tooth 200.

Referring now to FIG. 5 , a simplified top-down diagram of a pluralityof teeth 200 within the model 204 is shown according to an illustrativeembodiment. Each of the teeth 200 may be represented by the LAT 500.While shown as circular, it is noted that the LAT 500 may generallyfollow the outer profile for a respective tooth 200 and that circles areshown for representative purposes. The cut line determiner 124 may beconfigured to represent each of the lowest points 400 on the LAT 500.The cut line determiner 124 may be configured to define segments 502between each of the teeth 200 along the labial-labial (andlingual-lingual) division changes from the lowest points 400 between twoteeth 200. The cut line determiner 124 may be configured to join each ofthe segments 502 together along a respective side of the model (e.g.,adjacent labial-labial segments 502 and adjacent lingual-lingualsegments 502) to form a modified gingival line that extends betweenadjacent lowest points 400. The cut line determiner 124 may beconfigured to define a threshold distance from the lowest points 400 onthe labial and lingual side each tooth 200. The cut line determiner 124may define a perpendicular segment 504 at each lowest point 400 which isaligned with a centroid (for instance) of the respective tooth 200 andthe lowest point 400. The perpendicular segment 504 may extend radiallyoutwardly from the centroid and bisect the lowest point 400 on each sideof the tooth 200. The perpendicular segment 504 may extend a distancefrom the LAT 500 (such as, for instance, 1.5 mm). The outermost pointfrom the LAT 500 on the perpendicular segment 504 may be used forselecting points for the cut line 212. For instance, the points may bearranged between two outermost points on the perpendicular segment 504.In some embodiments, the points may be arranged parallel with thesegments 502. In other embodiments, the points may be located at adistance from the segments 502 but no closer to the segment than the twoadjacent outermost points on the adjacent perpendicular segments 504.

In some instances, a person may have missing teeth reflected in themodel 204. The cut line determiner 124 may be configured to compensatefor missing teeth within the model 204 by identifying a distance betweentwo adjacent LATs. Where the distance exceeds a threshold (e.g.,corresponding to an average distance between two adjacent teeth 200),the cut line determiner 124 may be configured to bridge the gap toconnect the cut line 212.

In each of these embodiments, the cut line determiner 124 is configuredto select points in the gingiva 202 a threshold distance from thegingival line 210 for forming the cut line 212. As can be best seen inFIG. 6 , which shows a perspective view of the model 204 focusing on theinterproximal region 600 between two teeth 200, in some implementations,the cut line 212 may not follow the interproximal region 600 between twoadjacent teeth 200. Rather, the cut line 212 may be “flat” such that thecut line 212 extends in a relatively straight line along theinterproximal region 600 between two teeth 200. Such embodiments mayprovide for a better fitting, more comfortable aligner 130.

In some embodiments, the cut line determiner 124 is configured togenerate multiple cut lines 212. The cut line 212 may be a first cutline 212, and the cut line determiner 124 can also generate a second cutline 216 and a third cut line 218. Each of the first cut line 212,second cut line 216, and third cut line 218 may be at a differentthreshold distance from the gingival line 210. The first cut line 212may be furthest from the gingival line 210, the third cut line 218 maybe nearest to the gingival line 210, and the second cut line 216 may bebetween the first cut line and the third cut line 218. In suchembodiments, the same model 204 may be used and reused for generating aplurality of dental aligners 130. For instance, three different types ofthermoforming materials may be thermoformed to the model 204 inaccordance with the sub-stages of the treatment plan. The first cut line212 may be used for cutting the first thermoforming materialthermoformed to the model 204, the second cut line 212 may be used forcutting the second thermoforming material subsequently thermoformed tothe model 204, and the third cut line 212 may be used for cutting thethird thermoforming material subsequently thermoformed to the model 204.By locating the cut line 212 at different threshold distances from thegingival line 210, the cutting tool 128 can cut into the model 204 alongeach cut line but the model 204 can still be reused for thermoformingand cutting subsequent dental aligners 130 without needing to cut orremove thermoformed material from the cut marks left in the model 204 bythe cutting tool 128 (e.g., since each subsequent cut is located closerto the gingival line 210). In other embodiments, the cut line determiner124 locates the cut line 212 at substantially the same position withrespect to the gingival line 210 and the cutting tool 128 is configuredto cut deeper for each subsequent cut from the same model 204 to removematerial that thermoforms into the cut marks left in the model 204during the previous cut.

The cut line determiner 124 may be configured to define the proximity ofthe cut line 212 with respect to the interproximal region 600 based on adetermined or selected percentage of the LAT used to define the gingivalmargin. In some embodiments, a user (such as a dental technician) maymodify one or more parameters (such as the percentage of the LAT, theintersection point between the LAT and gingival line 210, and so forth)to modify the proximity of the cut line 212 with respect to theinterproximal region 600. In some embodiments, the cut line 212 isflattened as lesser amounts of the LAT is used for defining the cut line212. For example, when the cut line 212 is defined based on using 100%of the LAT, the cut line 212 is more scalloped (e.g., the cut line 212significantly follows the curvature of the teeth 200 and extends deepestinto the interproximal region 600 between the teeth 200). In anotherexample, when the cut line 212 is defined based on using a lesser amountof the LAT, the cut line 212 is semi-scalloped (e.g., the cut line 212follows the curvature of the teeth 200 but only slightly extends intothe interproximal region 600 between the teeth 200). In another example,when the cut line 212 is defined based on using an even lesser amount ofthe LAT, the cut line 212 is flatter, flat, or substantially flatcompared to the scalloped or semi-scalloped cut lines 212 (e.g., the cutline 212 minimally follows the curvature of the teeth 200 and does notextent into the interproximal region 600 between the teeth 200, as shownin FIG. 6 ).

Referring now to FIG. 1 and FIG. 7 -FIG. 11 , the cut line determiner124 is configured to join the plurality of points together to form,generate, or otherwise define the cut line 212. FIG. 7 -FIG. 11 showvarious views of three-dimensional models 700, 800, 900, 1000corresponding to the model 204, according to illustrative embodiments.As described above, the cut line 212 extends around the model 204 anddefines a travel path 702 for the cutting tool 128 of the cutting system106. The travel path 702 extends outwardly from the model 204 at anangle that defines an angle of the cutting tool 128 with respect to thedental aligner 130. The angle may be an angle with respect to a normalvector from points of the cut line 212. Such an angle may be less than,for instance, 90°. In some embodiments, the angle may follow the normalvector. In some embodiments, the cut line determiner 124 may determinethe normal vector for each of the points of the cut line 212, and themay remove z-components of the normal vector (e.g., the z-componentextending parallel to the sagittal, or longitudinal plane) for definingthe angle of the cutting tool 128 with respect to the cut line 212. Thetip of the cutting tool 128 may be positioned along the outer edge 704,804, 904, 1004 of the travel path 702, 802, 902, 1002 and may extendtowards the dental aligner 130 and the model 204 at the angles shownextending outwardly from the models 700, 800, 900, 1000 and connectingthe cut line 212 to the outer edge 704, 804, 904, 1004.

In some embodiments, the cut line determiner 124 is configured to applya smoothing algorithm to smooth the cut line 212. The cut linedeterminer 124 is configured to apply the smoothing algorithm to variousportions of the cut line 212 or the entirety of the cut line 212. Thecut line determiner 124 may be configured to apply the smoothingalgorithm to smooth the cut line 212 adjacent to an interproximal regionbetween two teeth 200 of the model 204. Such areas may be prone to tear.Thus, the cut line determiner 124 may be configured to smooth the cutline 212 to eliminate steep cut-ins for the dental aligner 130 at theinterproximal region.

In some embodiments, the cut line determiner 124 is configured toidentify a rear (or terminal) molar 214 in the model 204. The cut linedeterminer 124 is configured to identify the rear molar 214 based on thenumber assigned to the teeth (e.g., by the tooth identifier 120). Thecut line determiner 124 is configured to identify the rear molar 214based on the last tooth present in the model 204 (which may or may notbe the third molar). The cut line determiner 124 is configured toconnect the cut line 212 for the outer portion of the dental aligner 130(e.g., the labial cut line 212 a) and the cut line 212 for the innerportion of the dental aligner 130 (e.g., lingual cut line 212 b). Hence,the cut line 212 may generally include a labial cut line 212 a andlingual cut line 212 b, and a connecting cut line 212 c that connectsthe labial cut line 212 a and the lingual cut line 212 b (as can be bestseen in FIGS. 10-11 ).

In some embodiments, the cut line determiner 124 is configured to definethe connecting cut line 212 c by wrapping the connecting cut line 212 caround the rear molar 214 (e.g. as shown in FIG. 11 ) within the gingiva202. In some embodiments, the cut line determiner 124 defines theconnecting cut line 212 c wrapping around the rear molar 214 to form afeature around the rear molar 214 in the gingiva portion 202 of thedental aligner 130. In some embodiments, the feature is formed byresting the cutting tool 128 on a portion of the gingiva portion 202 ofthe aligner 130 or by moving the cutting tool 128 back and forth acrossthe same cut line or within an area of the gingiva portion 202 of thealigner 130. In some embodiments, the feature is formed in a teethportion 134 of the aligner. The cut line determiner 124 may beconfigured to increase a space between the cut line 212 c and thegingiva line 210 to provide space for the cutting tool 128 to form thefeature. The feature can be used as an anchoring portion (e.g., for afixture tray or a manipulator component of the cutting tool 128). Insome embodiments, the feature is a portion of the aligner 130 thatincludes the material of the model 204 blended with a material of thealigner 130. The portion of the aligner 130 with blended material can belater removed during the fabrication process. In some embodiments, thecut line determiner 124 defines the connecting line 212 c taper theconnecting line 212 c around the rear molars 214 of the model 204.

In some embodiments, the cut line determiner 124 is configured to definethe connecting cut lines 212 c by crossing the connecting cut line 212 cover the top (e.g., the crown) of the rear molar 214. The connecting cutline 212 c may cross over a portion of the rear molar 214. In someembodiments, the cut line determiner 124 may cross the connecting cutline 212 c over half of the rear molar 214 (e.g., along themedial-distal center of the rear molar 214 as shown in FIG. 11 ) suchthat the connecting cut line 212 c bisects the rear molar 214.

In some embodiments, the cut line determiner 124 is configured toperform a collision analysis using an algorithm to determine whether thecutting tool 128 for the cutting system 106 will cut a non-cuttingportion of the dental aligner 130 (e.g., the teeth portion 132 forinterfacing with teeth 200). The collision analysis may include defininga ray extending through the cut line and at the angle of the travel path(e.g., at the angle defined by the outer edge 704 and the cut line 212).The collision analysis may include determining whether the rayintersects or contacts any non-cutting portions of the dental aligner130, such as teeth 200, the gingiva above the cut line 212, etc. Thecollision analysis may include re-defining the cut line responsive todetermining that the cutting tool 128 will cut a non-cutting portion ofthe dental aligner 130. The cut line determiner 124 may adjust variouspoints on the cut line 212 (e.g., including the distance between the cutline 212 and the gingival line 210) to prevent or avoid cutting anon-cutting portion of the dental aligner 130. The cut line determiner124 may adjust the angle of the cutting tool 128 (e.g., the angledefined by the travel path 702) to prevent or avoid cutting anon-cutting portion of the dental aligner 130.

Once the cut line 212 is defined, the cutting system controller 126 isconfigured to control a cutting tool 128 of the cutting system 106 tocut the dental aligner 130 along the cut line 212 to prepare the dentalaligner 130 for use. The cutting tool 128 may include a laser, a router,a CNC system, or other tool or system configured to cut a dental aligner130. The cutting system 106 may include various actuators forcontrolling motion of the cutting tool 128. The cutting tool 128 may beconfigured to operate over various degrees for freedom, such as four,five, or six or more degrees of freedom. The cutting system controller126 is configured to communicate signals to the actuators to controlmotion of the cutting tool 128. The cutting system controller 126 movesthe cutting tool 128 to a starting position at the outer edge 704 andangles the cutting tool 128 with respect to the cut line 212 (e.g.,toward the cut line 212). The cutting system controller 126 isconfigured to control the cutting tool 128 to cut the dental aligner 130along the cut line 212 following the cut line 212 at the outer edge 704.Following the dental aligner 130 being cut, the dental aligner 130 maybe cleaned, packaged, and shipped (e.g., either by itself or as part ofa group of aligners 130) to a user. The user may wear the aligners 130to adjust the position of the user's teeth according to the treatmentplan.

Referring now to FIG. 12 , a flowchart of a method 1200 for defining acut line 212 is shown according to an illustrative embodiment. Themethod 1200 and corresponding description is one method that can be usedfor defining a cut line 212. The model analyzer 118 is configured to usethe method 1200 or any other method to define the cut line 212.

At operation 1205, the tooth identifier 120 extracts teeth and gingivafrom a model. The model may be a three-dimensional model of a user'steeth or dentition. The model may be generated by the model generator116 based on dentition scans 108 captured via the dentition scanningsystem 104. The dentition scans 108 may be direct scans of a patient'sdentition, or scans of a physical model or impression of the patient'sdentition. The tooth identifier 120 extracts the teeth and gingiva byidentifying features which are typically associated with teeth 200(e.g., crowns on molars, separation or areas in an interproximal region,etc.) The tooth identifier 120 may identify teeth based on suchcharacteristics and features, and assign the remaining portions of themodel to the gingiva 202.

At operation 1210, the gingival line extractor 122 creates the gingivalline 210 within the model. The gingival line 210 is defined as theintersection or juncture between the teeth 200 and gingiva 202 withinthe model.

At operation 1211, the gingival line extractor 122 locates theintersection contours between teeth 200 and gingiva 202 in the model. Ascan be best seen in FIG. 2 (e.g., in a top view), the intersectioncontours may be the contours which follow the shape of the teeth. Forexample, the gingival line extractor 122 may project the intersectioncontours onto a two-dimensional top down view. The intersection contoursmay follow an outer surface contour of each of the teeth (e.g., along atransverse plane of the teeth). The gingival line extractor 122 mayidentify the intersection contours by locating the juncture between theteeth 200 and gingiva 202. The gingival line extractor 122 may thusidentify the intersection contours as the contours which define thegingival line 210.

At operation 1212, the gingival line extractor 122 identifies an archline 208. The gingival line extractor 122 may identify the centroids 206for each of the teeth 200. The gingival line extractor 122 may identifythe centroids 206 by identifying the center of mass of each of the teeth200. The gingival line extractor 122 may connect each of the centroids206 to identify the arch line 208. For example, the arch line 208 maytrace the centroids of the teeth 200. In some embodiments, the gingivalline extractor 122 may expand a width of the arch line 208 within thetop-down view (e.g., to create a polygon rather than a line). Thegingival line extractor 122 may expand the width of the arch line 208 toeliminate or lessen the likelihood of the interproximal region betweenteeth affecting the arch line by creating multiple disjoint regions. Insome embodiments, the gingival line extractor 122 may identify the archline 208 using other methods or algorithms, such as using theintersection contours in constructing the arch line 208 and defining thearch line 208 via a high-order function.

At operation 1213, the gingival line extractor 122 unites the teeth 200with the arch line 208. The gingival line extractor 122 may unite thetwo-dimensional teeth (e.g., within the top down view, such as the viewshown in FIG. 2 ) with the arch line 208 identified at operation 1212.The gingival line extractor 122 may snap each of the teeth 200 to thearch line 208. The gingival line extractor 122 may snap the teeth 200 tothe arch line 208 at their centroids 206. The gingival line extractor122 may union the teeth 200 with the arch line 208 to create a singlegingival line 210.

At operation 1214, the gingival line extractor 122 manipulates thegingival line 210 to join each of the teeth 200 together. For example,the gingival line extractor 122 may erode-dilate-erode the gingival line210. The gingival line extractor 122 may erode the gingival line (e.g.,decrease the size of the gingival line 210, or shrink the gingival line210) to smooth the shape of the gingival line 210. The gingival lineextractor 122 may dilate the gingival line 210 (e.g., expand or increasethe size of the gingival line 210) an amount or percentage (e.g., 10%,20%, 50%) to connect neighboring teeth 200 (even without the arch line208 being united with the teeth 200). The gingival line extractor 122may then erode the gingival line 210 to a size similar to or the same asthe gingival line 210 prior to execution of operation 1214 (e.g., backto the original size). Each of the teeth may be joined together due toeroding-dilating-eroding the gingival line 210.

At operation 1215, the cut line determiner 124 expands the gingival line210 across the surface of the model 204 to create the cut line 212. Thecut line determiner 124 expands the gingival line 210 across the surfaceof the model 204 to create the cut line 212 for the model 204.

At operation 1216, the cut line determiner 124 expands the gingival line210 across the surface of the model. The cut line determiner 124identifies points a distance within the gingiva 202 from the gingivalline 210. The distance may be, for instance, 1.00 mm, 2.00 mm, 2.50 mm,4.00 mm, etc., from the original position of the gingival line 210.Thus, the gingival line 210 is expanded into the gingiva 202 from thegingival line 210 and tracks the shape of the teeth 200. The cut linedeterminer 124 expands the gingival line 210 across the surface in thethree-dimensional model (e.g., shown in FIG. 7 -FIG. 11 ). For eachpoint on the gingival line 210, the cut line determiner 124 may generatea rectangle with a surface normal corresponding to a tangent of thegingival line 210 at the respective point. The cut line determiner 124may locate intersection edges between the gingiva 202 and the generatedrectangle. The cut line determiner 124 may trace from a point on thegingiva line 210 along the gingiva 202 until the expansion distance isreached (thus expanding the gingival line 210 into the gingiva 202 alongthe surface of the model).

At operation 1217, the cut line determiner 124 removesself-intersections of the expanded gingival line 210. Self-intersectionsinclude intersections between the gingival line 210 for one tooth as itis expanded into the gingiva 202 and the gingival line 210 for anadjacent tooth. The cut line determiner 124 may convert the gingivalline 210 to a two-dimensional representation to remove theself-intersections. Viewing the top down view shown in FIG. 2 , wherethe gingival line 210 for each of the teeth is expanded outwardly, thegingival line 210 of one tooth may intersect with a neighboring tooth orneighboring gingival line 210. The cut line determiner 124 removesoverlapping portions of the gingival line 210 at intersections of theoverlapping portions of the gingival line 210. Thus, the cut linedeterminer 124 removes the self-intersections and overlapping portionsof the expanded gingival line 210 such that the expanded gingival line210 tracks the shape of the teeth except near the interproximal regionwhere intersections would likely occur.

At operation 1218, the cut line determiner 124 snaps, overlays, draws,covers, or otherwise incorporates the expanded gingival line 210 intothe model 204 to create the cut line 212. For each point on thetwo-dimensional gingival line 210 (e.g., shown in FIG. 2 ), the cut linedeterminer 124 may perform a distance weighted averaging with thethree-dimensional points (e.g., within the model generated via the modelgenerator 116) to assign a z-value. In some embodiments, the cut linedeterminer 124 applies a smoothing algorithm to the two-dimensionalgingival line 210 with the assigned z-values. The cut line determiner124 may incorporate the two-dimensional gingival line 210 with z-valuesinto the three-dimensional model to define the cut line 212.

At operation 1220, the cut line determiner 124 moves the cut line 212over the rear molars 214. The cut line determiner 124 may identify therear molars 214 based on the number assigned to the teeth (e.g., by thetooth identifier 120 described above). The cut line determiner 124 mayidentify the rear molar 214 based on the last tooth present in the model204 (which may or may not be the third molar). The cut line determiner124 connects the cut line 212 for the outer portion of the dentalaligner 130 (e.g., the labial cut line 212 a) and the cut line 212 forthe inner portion of the dental aligner 130 (e.g., lingual cut line 212b). The cut line determiner 124 connects the cut lines 212 a, 212 b bycrossing the cut line 212 over the top (e.g., the crown) of the rearmolar 214. The cut line 212 may cross over a portion of the rear molar(such as half of the rear molar 214). The cut line determiner 124 maycross the cut line 212 over the rear molars 214 such that the cut line212 bisects the centroid 206 for the rear molars 214. Such embodimentsmay increase comfort of the resulting dental aligners 130 when worn bythe user.

At operation 1225, the cut line determiner 124 analyzes the cut line212. The cut line determiner 124 may analyze the cut line 212 todetermine whether any cuts will cut a non-cutting portion of the dentalaligners 130. The non-cutting portion includes, for instance, portionsof the aligner 130 which surround or are adjacent to teeth. For example,the non-cutting portion of the dental aligners 130 may include each ofthe teeth portion 134 of the dental aligners 130, or portions of thedental aligners 130 which touch, surround, or interface with the teethof the user. The cut line determiner 124 may perform a collisionanalysis to determine whether the cutting tool 128 will cut thenon-cutting portion of the dental aligners 130. The cut line determiner124 calculates a derivative of the cut line 212. The cut line determiner124 smooths the derivate of the cut line 212. The cut line determiner124 then computes a vector associated with the cutting tool 128. Thevector is associated with the angle of the cutting tool 128 with respectto the dental aligner 130. The cut line determiner 124 computes thevector for each point on the derivative of the cut line 212. The cutline determiner 124 then removes all vertical components (e.g.,components which are parallel to the sagittal plane) of the cut line 212normal, thus eliminating cuts to non-cutting portions of dental aligners130.

Referring now to FIG. 13 , a flowchart of a method 1300 of cutting adental aligner 130 is shown according to an illustrative embodiment. Themethod 1300 may be implemented by any combination of the componentsdescribed herein.

At operation 1305, the gingival line extractor 122 identifies a gingivalline 210 in a model. Operation 1305 may be similar to operation 1210 ofthe method 1200 described with reference to FIG. 12 . For example, thegingival line extractor 122 identifies the intersection or juncturesbetween the teeth 200 and gingiva 202, which may define the gingivalline 210.

At operation 1310, the cut line determiner 124 generates points in thegingiva portions of the model 204 for defining the cut line 212. The cutline determiner 124 generates points by expanding each of the points ofthe gingival line 210 outwardly along the gingiva 202 a distance fromthe point's original location at the gingival line 210. The cut linedeterminer 124 may generate points a threshold distance (e.g., 1.00 mm,1.50 mm, 2.00 mm, 4.00 mm, etc.) in the gingiva 202 (e.g., an absolutedistance from or a surface distance from a centroid of a tooth) from thegingival line 210. The cut line determiner 124 may thus expand theidentified gingival line 210 (e.g., identified at operation 1305) acrossa surface of the model (e.g., within the gingiva 202) a distance fromthe gingival line 210. The expanded gingival line 210 is constructed ofthe plurality of selected points.

At operation 1315, the cut line determiner 124 joins the points togetherto define the cut line 212. The cut line determiner 124 joins each ofthe points moved outwardly a distance from the gingival line 210 tocreate the cut line 212. Thus, the cut line 212 may track or trace theshape of the gingival line 210. In some embodiments, the cut linedeterminer 124 may apply a smoothing algorithm to smooth the cut line212 adjacent to the interproximal region between two teeth of the model204. Such areas may be prone to tear when used (e.g., worn) by the user.Thus, the cut line determiner 124 may smooth the cut line 212 toeliminate steep cut-ins on the dental aligner 130 at interproximalregions to eliminate or decrease the likelihood of the dental aligners130 tearing near or at interproximal areas.

In some embodiments, the cut line determiner 124 may identify rearmolars 214 within the model. The cut line determiner 124 may connect anouter portion and an inner portion of the cut line 212 by crossing thecut lines over a portion of the rear molars. Such embodiments may besimilar to operation 1220 described with reference to FIG. 12 .

In some embodiments, the cut line determiner 124 performs a collisionanalysis algorithm to determine whether the cutting tool 128 of thecutting system 106 will cut a non-cutting portion (e.g., teeth withinthe model) of the dental aligner 130. In some embodiments, the cut linedeterminer 124 calculates vectors associated with the cutting tool 128with respect to the dental model 204 and uncut dental aligner 130 (e.g.,which may be substantially the same as the normal vector of each pointfor the cut line 212 extending from the gingiva 202). The cut linedeterminer 124 may determine whether there are any vertical componentsof the vector (e.g., components of the vector extending parallel to thesagittal plane), which may cause the cutting tool 128 to cut thenon-cutting portion of the dental aligner 130. The cut line determiner124 may re-define the cut line 212 to remove any vertical components ofthe vector. Such embodiments may eliminate or decrease the likelihood ofthe cutting tool 128 cutting a non-cutting portion of the dental aligner130.

The cut line 212 may be a line which extends around the model 204 anddental aligner 130 and defines a travel path for the cutting system 106,and more specifically a travel path for the cutting tool 128. The travelpath may extend outwardly from the model 204 and uncut dental aligner130 at an angle which defines the angle of the cutting tool 128 withrespect to the model 204 and uncut dental aligner 130 (e.g., the vectordescribed above).

At operation 1320, the cutting system controller 126 may control thecutting system 106 to cut the dental aligner 130 along the cut line 212.The cutting system controller 126 controls the cutting system 106 todirect the cutting tool along the travel path 702 to cut the dentalaligner 130 while on the model 204 along the cut line 212. The cuttingsystem controller 126 may communicate a starting position (e.g., a firstpoint along the cut line 212) and a vector for the cutting tool 128, andthe travel path 702. The cutting system 106 may move the cutting tool128 to the starting position and with the vector, initiate the cuttingtool 128, and move the cutting tool 128 along the travel path 702.Alternatively, the cutting system controller 126 may control actuatorswithin the cutting system 106 directly to manipulate movement of thecutting tool 128.

Referring now to FIG. 15 , an illustration of a model 1500 of a user'sdentition is shown according to an illustrative embodiment. In someembodiments, the cut line determiner 124 may be configured to determinethe cut line 212 based on the reference point 206. As described above,the tooth identifier 120 may be configured to determine a referencepoint 206 for each tooth 200 of the model 1500. In some embodiments, thereference point 206 may be a center or centroid of the tooth 200, asshown in FIG. 2 . In some embodiments, the reference point 206 may be acenter of a LAT 500, as shown in FIG. 5 . For example, the toothidentifier 120 may be configured to compute, calculate, determine, orotherwise identify the reference point 206 by computing an average orcenter of points that define a LAT 500.

The cut line determiner 124 may be configured to determine a lowestpoint 400 as described above with reference to FIG. 4 . In someembodiments, the cut line determiner 124 may be configured to determinea lowest point 400 on both the labial and lingual sides of the teeth.The cut line determiner 124 may be configured to connect the referencepoint 206 and lowest point 400 using a connector 1502 (shown as an arrowextending from the lowest point 400 to the reference point 206). In someembodiments, the connector 1502 is disposed on a plane including thelowest point 400. The cut line determiner 124 may be configured todefine a cut plane 1504 along the connector 1502 for determining,calculating, or otherwise defining the cut line 212, as described ingreater detail below.

Referring now to FIG. 15 -FIG. 19 , the cut line determiner 124 may beconfigured to determine or identify a distance 1506 from the lowestpoint 400. Specifically, FIG. 16 -FIG. 17 show illustrations of themodel 1500 having a cut line 1600 defined based on a first distance1506, FIG. 18 shows the model 1500 with a second distance 1507 (which isless than the first distance 1506), and FIG. 19 shows a model 1500having a cut line 1900 based on the second distance 1507. The distance1506, 1507 may be or include a distance from the lowest point 400 alongthe connector 1502. In some embodiments, the distance 1506 may be adefault distance (for example, 0.5 mm, 1 mm, 2 mm, etc.). In someembodiments, the distance 1506 may be a variable distance. The distance1506, 1507 may be set based on an analysis of the dental arch from themodel 1500. For example, the distance may decrease as a complexity oftreatment increases (e.g., where the teeth 200 are more crowded forexample). In some implementations, the cut line determiner 124 may beconfigured to receive a classification of the model 1500 (e.g., from thetreatment planner 114, for instance). The cut line determiner 124 may beconfigured to determine the distance 1506, 1507 based on theclassification of the model 1500. In some embodiments, the distance1506, 1507 may change on a tooth-by-tooth basis. In some embodiments,the distance 1506, 1507 may be a constant across each of the teeth. Insome embodiments, the distance 1506, 1507 may be a constant on bothlabial and lingual sides of the tooth 200 (e.g., the distance 1506, 1507from the labial-side lowest point 400 may be the same as the distance1506, 1507 from the lingual-side lowest point 400). As described ingreater detail below, the distance 1506, 1507 may define a number orportion of points from the LAT 500 which are included in the cut line212. As shown in FIG. 16 and FIG. 17 in comparison to FIG. 19 , as thedistance 1506 from the lowest point 400 decreases, the cut line 212correspondingly flattens (e.g., to become less curvy, sloped, wavy,rounded, or curvilinear), such that the cut line 1600 shown in FIG. 16and FIG. 17 is more curved than the cut line 1900 shown in FIG. 19 .Accordingly, the distance 1506, 1507 may cause the cut line 1600 to havea scalloped shape.

The cut line determiner 124 may be configured to define a cut plane 1504using the determined or identified distance 1506, 1507. The cut linedeterminer 124 may be configured to define a cut plane 1504 for eachtooth within the model 1500. The cut line determiner 124 may beconfigured to define a cut plane 1504 for the labial and lingual side ofeach tooth of the model 1500. The cut plane 1504 may be or include aplane that extends at an angle relative to the connector 1502. The cutplane 1504 may be defined along the connector 1502 at the distance 1506,1507 from the lowest point 400. For example, where the distance 1506 is1.0 mm, the cut line determiner 124 may define the cut plane 1504 alongthe connector 1502 at 1.00 mm from the lowest point 400. In someembodiments, the cut plane 1504 may extend perpendicular or orthogonalto the connector 1502. The cut line determiner 124 may define the cutplane 1504 along the connector 1502 beginning at the distance 1506, 1507from the lowest point 400 and extending radially outwardly (e.g.,perpendicular or orthogonal) from the connector 1502 towards the LAT500.

The cut line determiner 124 may be configured to identify LAT points1508 on the LAT 500 that are bisected, contacted, or otherwise locatedon the cut plane 1504. As shown in FIG. 15 , the LAT points 1508 arelocated on opposing sides of the cut plane 1504 at the intersectionbetween the cut plane 1504 and the LAT 500. The cut line determiner 124may be configured to use the LAT points 1508 for defining the cut line212.

The cut line determiner 124 may be configured to identify, select, orotherwise determine points on the LAT 500 for defining the cut line 212.The cut line determiner 124 may determine points on the LAT 500 that arebetween each of the LAT points 1508. The cut line determiner 124 maydetermine points on the LAT 500 which are “below” the cut plane 1504(e.g., on a gingival-side of the cut plane 1504). For example, on thelabial side of a tooth 200, the cut line determiner 124 may beconfigured to determine points on the LAT 500 that are between the LATpoints 1508 on the gingival-side of the cut plane 1504 and include thelabial-side lowest point 400. As the distance 1506 increases, morepoints are determined by the cut line determiner 124 for determining ordefining the cut line 212. The cut line determiner 124 may determine oridentify points on the LAT 500 for each tooth 200, and for both labialand lingual sides of each tooth 200, based on the cut plane 1504 definedfor each tooth 200 (e.g., both on the labial and lingual side).

The cut line determiner 124 may define the cut line 212 based on theselected or determined points for each tooth 200. The cut linedeterminer 124 may define the cut line 212 to include each of thedetermined points that are located on the gingival-side of the cut plane1504. The cut line determiner 124 may define the cut line 212 to connectlabial and lingual points for two adjacent teeth 200 (e.g., labial-sidepoints determined for a first tooth 200 connecting labial-side pointsdetermined for a second tooth 200 adjacent to the first tooth 200, andlingual-side points determined for a first tooth 200 connectinglingual-side points determined for a second tooth 200 adjacent to thefirst tooth 200). The cut line determiner 124 may define the cut line212 within an interproximal region between two adjacent teeth 200, whichconnects determined/identified points for the two adjacent teeth 200. Insome embodiments, the cut line determiner 124 may define the cut line212 within the interproximal region by identifying a straight line thatconnects the LAT points 1508 that face each other on two adjacent teeth200. The cut line determiner 124 may define the cut line 212 within theinterproximal region by applying the straight line on the surface of thegingiva of the model 1500 (e.g., thereby producing a semi-curved line asa result of a straight line being applied on a sloped or non-flatsurface). The cut line determiner 124 may define the cut line 212 toconnect labial and lingual cut lines in a manner as described above withreference FIG. 10 -FIG. 11 ).

Referring now to FIG. 20 -FIG. 21 , in some embodiments, the cut linedeterminer 124 may be configured to receive an offset value for definingan offset distance 2000 of the cut line 2002 from a gingiva-toothinterface of the model 1500. Specifically, FIG. 20 shows an illustrationof the model 1500 having a cut line 2002 at a first offset distance2000, and FIG. 21 shows an illustration of the model 1500 having a cutline 2002 at a second offset distance 2000. The offset may move the cutline 2002 either toward a crown of a tooth or into the gingiva of thetooth. In some embodiments, the cut line determiner 124 may beconfigured to receive the offset value from a computing device (such asa computing device associated with the treatment planner 114, associatedwith the dentition scanning system 104, etc.). In some embodiments, theoffset value may be a fixed value for each of the teeth in the model1500 (e.g., for each teeth, both on the labial-side and the lingualside). In some embodiments, the cut line determiner 124 may beconfigured to receive or otherwise determine a variable offset value.For example, and similar to the embodiments described above withreference to the distance 1506, 1507, the cut line determiner 124 may beconfigured to receive or determine a variable offset value based on acomplexity of treatment (e.g., crowding, malocclusion, etc.), based on aclassification of the model 1500, etc. In some embodiments, the cut linedeterminer 124 may be configured to receive or determine the variableoffset value on a tooth-by-tooth basis (e.g., to change the offset valueas teeth are more crowded, for example). In some embodiments, the cutline determiner 124 may be configured to receive or determine thevariable offset value on a labial or lingual-side basis. For example,the labial-side cut line may have a first offset value and the lingualside cut line may have a second offset value. As such, variousimplementations and embodiments of offset values and distances 1506,1507 may be determined (in some instances, on a tooth-by-tooth basis)for each individual model 1500, to both provide increased comfort, lessresistance to tearing, and/or to impart forces on teeth for treatment.In some embodiments, a first algorithm is used to generate a firstpreliminary cut line and a second algorithm different from the firstalgorithm is used to generate a second preliminary cut line, and thenthe cut line determiner 124 uses part of the first preliminary cut lineand part of the second preliminary cut line to create the cut line 2002.For example, the cut line determiner 214 can generate a firstpreliminary cut line having a positive offset distance and generate asecond preliminary cut line having a negative offset distance, and thengenerate the cut line 2002 using the first preliminary cut line for oneor more teeth and using the second preliminary cut line for one or moreteeth. In some embodiments, the cut line determiner 214 uses the firstpreliminary cut line for each tooth as a default and uses the secondpreliminary cut line for individual teeth that are selected by a userinput (e.g., based on a user input from a dentist, orthodontist, ortechnician).

The cut line determiner 124 may be configured to define the cut line 212based on the offset value. The cut line determiner 124 may be configuredto compute cut line points based on the defined/determined points andthe received offset value. For example, the cut line determiner 124 maybe configured to compute the cut line points by moving each of thedefined/determined points an offset distance 2000 along a surface of themodel 1500 based on the offset value. As shown in FIG. 20 and FIG. 21 ,the offset value may be a positive or negative value, respectively.Where the offset value is a positive value, the cut line determiner 124may compute the cut line points at an offset distance 2000 within thegingiva portion of the model 1500. Similarly, where the offset value isa negative value, the cut line determiner 124 may compute the cut linepoints at an offset distance 2000 within the teeth portion of the model1500. In some embodiments, the cut line determiner 124 may compute thecut line points by shifting, for each point defined or identified asdescribed above on the LAT 500 and in the interproximal region, thepoint on or along the surface of the model 1500 in the y-z direction(e.g., where they direction is along the longitudinal axis of the body,and the z direction is along the sagittal axis of the body).

Referring now to FIG. 2 and FIG. 22 , and in some instances where aparticular model 1500 includes a void or space between teeth 200 withinthe interproximal region, the model generator 116 may be configured toadd, incorporate, or otherwise provide interproximal virtual fillerwithin the void or space between two adjacent teeth 200. Specifically,FIG. 22 shows an illustration of a model 1500 of a user's dentitionincluding interproximal virtual filler 2200, 2202. The model generator116 may be configured to provide labial and lingual-side interproximalvirtual filler 2200, 2202, respectively. The cut line determiner 124 maybe configured to define the cut line 2204 using the interproximalvirtual filler 2200, 2202, as described in greater detail below.

In some embodiments, the model generator 116 may be configured toidentify or determine a centroid 206 for each tooth 200 within the model204. In some embodiments, the model generator 116 may be configured todetermine the centroid 206 by averaging the locations of each of thevertices of the tooth 200 (e.g., similar to calculating or computing acenter of mass for an object of uniform density). The model generator116 may be configured to determine, compute, or otherwise define a threedimensional vector (shown as a connector 208, and referred to herein as“NX”) beginning at a centroid 206 (referred to herein as “C0”) of afirst tooth 200 connecting each of the other centroids 206 (referred toherein as “C1”-“CN”) of a dental arch. The model generator 116 mayselect, determine, or otherwise identify adjacent teeth 200 from a giventooth 200 by identifying a centroid C1 of a neighbor tooth 200 (referredto as neighbor 0 (N0)) having a shortest straight line distance alongthe connector 208 from the C0 of the given tooth 200 (referred to asadjacent 0 (A0)). The model generator 116 may be configured to compute,calculate, or otherwise determine a unit vector U0 from C0 to A0, and anadjacent direction vector (D0). For the next neighbor tooth 200 (e.g.,N1), the model generator 116 may be configured to compute, calculate, orotherwise determine the unit vector (U1) between the centroid C0 and thecentroid C1 of the next neighbor tooth N1. The model generator 116 maybe configured to compute, determine, or otherwise calculate a dotproduct (e.g., by performing a dot product operation) between U0 and U1.Where the dot product is greater than −0.25, than the model generator116 may be configured to define N1 as the next adjacent tooth 200 (e.g.,adjacent tooth A1), and define the unit vector U1 to be the nextadjacent direction vector (D1). If the dot product is not greater than−0.25, the model generator 116 may be configured to repeat computing theunit vector with the next adjacent tooth (N1+1). Following determiningA1 and D1, model generator may be configured to add, incorporate, orotherwise provide C0, A0, D0, A1 and D1 to a data structure (such asmemory 112) labeled with the centroid C0's unique location coordinates(referred to herein as adjacency information “Adj Set” for adjacencyset). The model generator 116 may be configured to repeat theabove-mentioned steps until each of the centroids 206 have been proceed,thereby generating an Adj Set for each of the centroids 206 of the model204.

The model generator 116 may be configured to define the labial andlingual-side virtual filler 2200, 2202 by defining two two-dimensional(2D) planes for each centroid pair 206 (e.g., of two adjacent teeth200). The model generator 116 may be configured to define the two 2Dplanes that are each centered at each of centroids in the pair. Themodel generator 116 may be configured to orient the 2D planes such thata normal vector of each of the 2D planes align with the unit vector Uwhich points towards the other centroid 206 in the pair. The modelgenerator 116 may be configured to perform an intersection Booleanoperation between the 2D planes and the tooth 200 models whose centroids206 that they are centered at, which result in two two-dimensionalprofiles of the neighboring teeth 200 within the labial and lingualsides of the interproximal region. The model generator 116 may beconfigured to scale the 2D profiles to between 60%-80% their initialsize. The model generator 116 may be configured to perform an edge loopbridging function to join the two 2D profiles together forming athree-dimensional object having a labial and lingual side virtual filler2200, 2202, which acts to fill the gaps between the teeth. The modelgenerator 116 may be configured to repeat this for each centroid pair206 until each of the teeth 200 have been processed, such that virtualfiller is added between each of the teeth 200 where gaps would otherwisebe present.

The cut line determiner 124 may be configured to define the cut line 212along the interproximal virtual filler 2200, 2202 between two adjacentteeth 200. The cut line determiner 124 may be configured to define thecut line 212 within the interproximal region, by drawing a straight linebetween the LAT points 1508 for two adjacent teeth, and applying thestraight line to the curved surface within the interproximal region onor along the interproximal virtual filler 2200, 2202 between twoadjacent teeth. Such embodiments may provide for a dental aligner 130that has a negative offset, but still comfortably fits on a patient'steeth, particularly where the patient's teeth have a gap in theinterproximal region between two teeth that are angled towards eachother.

As utilized herein, the terms “approximately,” “about,” “substantially,”and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the disclosure as recited inthe appended claims.

It should be noted that the term “exemplary” and variations thereof, asused herein to describe various embodiments, are intended to indicatethat such embodiments are possible examples, representations, orillustrations of possible embodiments (and such terms are not intendedto connote that such embodiments are necessarily extraordinary orsuperlative examples).

The term “coupled” and variations thereof, as used herein, means thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent or fixed) or moveable (e.g.,removable or releasable). Such joining may be achieved with the twomembers coupled directly to each other, with the two members coupled toeach other using a separate intervening member and any additionalintermediate members coupled with one another, or with the two memberscoupled to each other using an intervening member that is integrallyformed as a single unitary body with one of the two members. If“coupled” or variations thereof are modified by an additional term(e.g., directly coupled), the generic definition of “coupled” providedabove is modified by the plain language meaning of the additional term(e.g., “directly coupled” means the joining of two members without anyseparate intervening member), resulting in a narrower definition thanthe generic definition of “coupled” provided above. Such coupling may bemechanical, electrical, or fluidic.

The term “or,” as used herein, is used in its inclusive sense (and notin its exclusive sense) so that when used to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is understood to convey that anelement may be X, Y, or Z; X and Y; X and Z; Y and Z; or X, Y, and Z(i.e., any combination of X, Y, and Z). Thus, such conjunctive languageis not generally intended to imply that certain embodiments require atleast one of X, at least one of Y, and at least one of Z to each bepresent, unless otherwise indicated.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below”) are merely used to describe the orientation of variouselements in the figures. It should be noted that the orientation ofvarious elements may differ according to other exemplary embodiments,and that such variations are intended to be encompassed by the presentdisclosure.

The hardware and data processing components used to implement thevarious processes, operations, illustrative logics, logical blocks,modules, and circuits described in connection with the embodimentsdisclosed herein may be implemented or performed with a general purposesingle- or multi-chip processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. A generalpurpose processor may be a microprocessor, or any conventionalprocessor, controller, microcontroller, or state machine. A processoralso may be implemented as a combination of computing devices, such as acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. In some embodiments, particularprocesses and methods may be performed by circuitry that is specific toa given function. The memory (e.g., memory, memory unit, storage device)may include one or more devices (e.g., RAM, ROM, flash memory, hard diskstorage) for storing data and/or computer code for completing orfacilitating the various processes, layers and circuits described in thepresent disclosure. The memory may be or include volatile memory ornon-volatile memory, and may include database components, object codecomponents, script components, or any other type of informationstructure for supporting the various activities and informationstructures described in the present disclosure. According to anexemplary embodiment, the memory is communicably connected to theprocessor via a processing circuit and includes computer code forexecuting (e.g., by the processing circuit or the processor) the one ormore processes described herein.

The present disclosure contemplates methods, systems, and programproducts on any machine-readable media for accomplishing variousoperations. The embodiments of the present disclosure may be implementedusing existing computer processors, or by a special purpose computerprocessor for an appropriate system, incorporated for this or anotherpurpose, or by a hardwired system. Embodiments within the scope of thepresent disclosure include program products comprising machine-readablemedia for carrying or having machine-executable instructions or datastructures stored thereon. Such machine-readable media can be anyavailable media that can be accessed by a general purpose or specialpurpose computer or other machine with a processor. By way of example,such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, orother optical disk storage, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to carry or storedesired program code in the form of machine-executable instructions ordata structures and which can be accessed by a general purpose orspecial purpose computer or other machine with a processor. Combinationsof the above are also included within the scope of machine-readablemedia. Machine-executable instructions include, for example,instructions and data which cause a general purpose computer, specialpurpose computer, or special purpose processing machines to perform acertain function or group of functions.

Although the figures and description may illustrate a specific order ofmethod steps, the order of such steps may differ from what is depictedand described, unless specified differently above. Also, two or moresteps may be performed concurrently or with partial concurrence, unlessspecified differently above. Such variation may depend, for example, onthe software and hardware systems chosen and on designer choice. Allsuch variations are within the scope of the disclosure. Likewise,software implementations of the described methods could be accomplishedwith standard programming techniques with rule-based logic and otherlogic to accomplish the various connection steps, processing steps,comparison steps, and decision steps.

It is important to note that the construction and arrangement of thesystems and methods shown in the various exemplary embodiments areillustrative only. Additionally, any element disclosed in one embodimentmay be incorporated or utilized with any other embodiment disclosedherein.

What is claimed is:
 1. A method of cutting a dental aligner, the methodcomprising: identifying, for a plurality of teeth of a model, aplurality of interface points disposed on a respective tooth-gingivainterface of the plurality of teeth and a plurality of reference pointsfor each of the plurality of teeth; defining a plurality of cut planes,wherein a cut plane for a respective tooth extends between two interfacepoints for the respective tooth at a distance from the reference pointfor the respective tooth; identifying a subset of the plurality ofinterface points based on the plurality of cut planes; defining a cutline based on the subset of the plurality of interface points; andcontrolling a cutting system to cut the dental aligner along the cutline.
 2. The method of claim 1, wherein the plurality of interfacepoints include a first plurality of interface points for a first tooth,wherein the first plurality of interface points are identified based ona line around tooth (LAT) for the first tooth.
 3. The method of claim 1,wherein the plurality of reference points are a plurality of centroidsfor the plurality of teeth.
 4. The method of claim 1, wherein a numberof interface points for a respective tooth included in the subset of theplurality of interface points decreases as the distance between the cutplane and the reference point for the respective tooth increases.
 5. Themethod of claim 1, wherein defining the cut line is based on the subsetof the plurality of interface points and an offset applied to the cutline.
 6. The method of claim 1, wherein defining the cut line comprisesconnecting a first reference point for a first tooth and a secondreference point for a second tooth along an interproximal space betweenthe first tooth and the second tooth, the first reference point and thesecond reference point included in the subset.
 7. The method of claim 6,wherein the first reference point and the second reference point areconnected via a straight line along an interproximal surface of theinterproximal space.
 8. The method of claim 7, further comprisinggenerating an interproximal virtual filler between the first tooth andthe second tooth, wherein the interproximal surface is located along theinterproximal virtual filler between the first tooth and the secondtooth.
 9. The method of claim 1, wherein defining the plurality of cutplanes comprises defining a first plurality of cut planes for a labialside of the plurality of teeth and defining a second plurality of cutplanes for a lingual side of the plurality of teeth.
 10. The method ofclaim 1, wherein the cut plane for a respective tooth is perpendicularto a line extending between the reference point for the respective toothand an interface point for the respective tooth.
 11. A system forcutting a dental aligner, the system comprising: a cut line systemconfigured to: identify, for a plurality of teeth of a model, aplurality of interface points disposed on a respective tooth-gingivainterface of the plurality of teeth and a plurality of reference pointsfor each of the plurality of teeth; define a plurality of cut planes,wherein a cut plane for a respective tooth extends between two interfacepoints for the respective tooth at a distance from the reference pointfor the respective tooth; identify a subset of the plurality ofinterface points based on the plurality of cut planes; and define a cutline based on the subset of the plurality of interface points; and acutting system including a cutting tool configured to cut the dentalaligner along the cut line.
 12. The system of claim 11, wherein theplurality of interface points include a first plurality of interfacepoints for a first tooth, wherein the first plurality of interfacepoints are identified based on a line around tooth (LAT) for the firsttooth.
 13. The system of claim 11, wherein the plurality of referencepoints are a plurality of centroids for the plurality of teeth.
 14. Thesystem of claim 11, wherein a number of interface points for arespective tooth included in the subset of the plurality of interfacepoints decreases as the distance between the cut plane and the referencepoint for the respective tooth increases.
 15. The system of claim 11,wherein defining the cut line is based on the subset of the plurality ofinterface points and an offset applied to the cut line.
 16. The systemof claim 11, wherein the cut line system is configured to define the cutline by connecting a first reference point for a first tooth and asecond reference point for a second tooth along an interproximal spacebetween the first tooth and the second tooth, the first reference pointand the second reference point included in the subset.
 17. The system ofclaim 16, wherein the first reference point and the second referencepoint are connected via a straight line along an interproximal surfaceof the interproximal space.
 18. The system of claim 11, wherein the cutline system is configured to define a first plurality of cut planes fora labial side of the plurality of teeth and define a second plurality ofcut planes for a lingual side of the plurality of teeth.
 19. Anon-transitory computer readable medium storing instructions that, whenexecuted by a processor, cause the processor to perform operations, theoperations comprising: identify, for a plurality of teeth of a model, aplurality of interface points disposed on a respective tooth-gingivainterface of the plurality of teeth and a plurality of reference pointsfor each of the plurality of teeth; define a plurality of cut planes,wherein a cut plane for a respective tooth extends between two interfacepoints for the respective tooth at a distance from the reference pointfor the respective tooth; identify a subset of the plurality ofinterface points based on the plurality of cut planes; define a cut linebased on the subset of the plurality of interface points; and generateone or more output signals to cause a cutting tool to cut a dentalaligner along the cut line.
 20. The non-transitory computer readablemedium of claim 19, wherein the plurality of interface points include afirst plurality of interface points for a first tooth, wherein the firstplurality of interface points are identified based on a line aroundtooth (LAT) for the first tooth, and wherein the plurality of referencepoints are a plurality of centroids for the plurality of teeth.